Although not well represented in the literature, day treatment programs targeting substance abuse problems have increased in both number and acceptability in recent years. This article reports on a day treatment program based on the Therapeutic Community (TC), and on outcomes for a sample of substance abuse clients (n = 66) entering the program. Participants were interviewed early in treatment and 6 months after admission using the Addiction Severity Index (ASI) and other measures. Clients entering day treatment were demographically diverse, with serious substance-abuse problems and psychiatric morbidity. Median retention in day treatment was about 5 weeks, but many clients received a contiguous episode of residential treatment, so that the median for total time in treatment was 18 weeks. Clients located and interviewed at 6-month follow-up (n = 38) showed significant improvement in alcohol and drug use, legal and social problems, and psychiatric symptoms. Findings suggest that day treatment can be used effectively as a precursor to residential treatment and that some clients applying for residential treatment can be treated effectively in day treatment alone.